PHOTOSTIMULATED EVAPORATION OF SIO2 AND SI3N4 FILMS BY SYNCHROTRON RADIATION AND ITS APPLICATION FOR LOW-TEMPERATURE CLEANING OF SI SURFACES

SiO2 and Si3 N4 films are shown to be removable by vacuum ultraviolet light irradiation with synchrotron radiation (SR) in an ultrahigh vacuum. The dependence of the photostimulated evaporation rate on substrate temperature shows that the reaction is induced by an electronic mechanism. Polycrystalline Si and crystal Si are unaffected by SR irradiation. By applying this reaction to the thin native oxide film grown during a wet pretreatment, Si surfaces can be cleaned at temperatures as low as 650-degrees-C. Si(100)-2 x 1 and Si(111)-7 x 7 structures are observed by reflection high-energy electron diffraction after a few hours irradiation. Two-dimensional epitaxial growth by gas-source molecular-beam epitaxy with Si2H6 occurs selectively on the SR-irradiated region of a Si(100) surface, indicating cleanliness and flatness of the irradiated area.